考虑形状记忆合金内部热效应的循环本构模型研究

In view of the deficiencies in experiment and theory considering the internal thermal effect of shape memory alloys(SMAs) under cyclic loading, the systematic macro experiments were carried out to find out the characteristics of cylic deformation and evolution laws of temperature of the material under different loading conditions and indicate the thermomechanical coupling mechanism between the phase transformation latent heat, intrinsic mechanical dissipation and cyclic deformation. In the thermodynamics framework,the new Helmholtz free energy expression and thermal equation are proposed to characterize phase transformation latent heat and intrinsic mechanical dissipation of SMAs, the reasonable internal variables and their evolution equations are introduced to describe the deformation behavior under cyclic loading, and then a cyclic constitutive model considering the internal thermal effect for SMAs is established based on the experimtental observations.A simple method of determining thermomechnical material parameters is proposed for the developed model and the reasonability of this model is validated through solving the problem of the thermomechanical boundary value and simulating the experimental results.This project focuses on the study of experiment and constitutive model of phase transformation materials considering the coupling effect between the internalthermal effect and deformation under cyclic loading, research findings are an important development to cyclic constitutive model of smart materials and have an important theoretical significance. The related research achievements can also be used in design, safety assessment and life prediction of SMAs-based components.

针对形状记忆合金在循环载荷下内部热效应实验和理论研究的不足，通过系统的宏观实验研究，了解材料在不同加载条件下的循环变形特性和温度演化规律，揭示相变潜热和本征机械耗散与循环变形的热力耦合作用机理。基于实验观测，在热力学框架下给出新的Helmholtz自由能表述和热方程来表征形状记忆合金的相变潜热和本征机械耗散，引入合理的内变量及其演化方程来描述循环载荷下的变形行为，进而建立考虑内部热效应的形状记忆合金循环本构模型。针对建立的本构模型，提出一套简单的热力学参数确定方法，通过求解热力耦合边界值问题对实验结果进行模拟，验证提出模型的合理性。本项目针对循环载荷下相变材料内部热效应与变形的耦合作用进行实验研究和本构模型研究，研究成果是对智能材料循环本构关系及其应用的重要拓展，研究具有重要的理论意义；同时，研究成果也可应用于形状记忆合金元器件的设计、安全评估和寿命预测。

针对镍钛形状记忆合金的热力耦合功能性疲劳和结构性疲劳行为开展了实验观测、本构模型研究和有限元模拟。首先，通过搭建的热力耦合实验平台获取材料单轴和非比例多轴循环变形特征和温度演化律，揭示了率相关相变棘轮行为的热力耦合作用机理；然后，基于实验观测，在晶体塑性框架下建立了多机制的单晶循环本构模型，通过显示过渡法则拓展到多晶情形，并结合一维平均温度场假设，建立了热力耦合循环本构模型；进而，在热力学框架下建立了宏观唯象的热力耦合循环本构模型，合理预测了不同加载速率下的相变棘轮行为。最后，对循环变形过程中马氏体相变带的演化进行了原位观测，结合热力耦合有限元分析结果，揭示了率相关马氏体相变图案的演化规律。近3年发表项目相关论文22篇，其中SCI收录14篇，EI论文4篇。培养博士生2名，硕士生2名。在国内学术会议做邀请报告1次，3次出国访问和合作研究。

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